Multilayer Insulator for Dual Free Layer Read Heads
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Solution Overview
Problem
Dual free layer (DFL) read heads face challenges in achieving higher areal density without compromising head stability and performance reliability due to the negative impact of using MgO as a read junction insulator on rear hard bias (RHB) coercivity.
Innovation Solution
A multilayer insulating structure is introduced between the DFL sensor and the RHB structure, with a layer composed of the same material as the TMR barrier (such as MgO) adjacent to the sensor and a different insulating material adjacent to the RHB, enhancing performance without lowering RHB coercivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If MgO is used as the read junction insulator to ensure chemical compatibility with the MgO TMR barrier, then higher areal density is achieved, but RHB coercivity is degraded
Solution Approach 1:
The insulating layer is divided into multiple segments: a first insulating layer (MgO) adjacent to the TMR barrier for chemical compatibility and areal density, and a second insulating layer (different material) adjacent to the RHB structure for maintaining coercivity. This segmentation allows each layer to perform its specific function without compromising the other.
Solution Approach 2:
The multilayer insulating structure acts as an intermediary between the TMR barrier and the RHB structure. The first layer (MgO) interfaces with the TMR barrier while the second layer (different material) interfaces with the RHB, mediating the interaction to achieve both chemical compatibility and coercivity maintenance.
2Device complexity
If a single layer insulator is used between the RHB and DFL sensor, then device complexity is reduced, but either chemical compatibility or RHB coercivity must be compromised
Solution Approach 1:
The insulating structure uses composite materials - a combination of MgO (first insulating layer) and a different insulating material (second layer). This composite structure provides both chemical compatibility with the TMR barrier and maintains RHB coercivity, achieving what a single material cannot accomplish alone.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The multilayer insulating structure improves areal density and maintains RHB coercivity, ensuring higher performance and stability of the DFL read head.
Implementation Method 1
the degradation due to chemical intermixing between the junction insulator and the TMR barrier made of different atomic elements can be prevented
Implementation Method 2
a permanent magnetic or rear hard bias (RHB) structure that delivers twice as high of a readout amplitude
Implementation Method 3
the two free layers individually stabilized longitudinally by antiferromagnetically coupled (AFC) soft bias (SB) structures
Implementation Method 4
TMR sensors, which include MgO as a barrier layer, show great performance because of the higher TMR value and signal to noise ratio
Data Source
AI summary
The present disclosure generally related to read heads having dual free layer (DFL) sensors. The DFL sensor and has a surface at the media facing surface (MFS). Behind the DFL sensor away from the MFS, is a rear hard bias (RHB) structure. The RHB structure is disposed between the shields as well. In between the DFL sensor and the RHB structure is insulating material. The insulating material is a multilayer structure. A first layer of the multilayer structure is composed of the same material as the tunnel magnetoresistive barrier layer, such as MgO, and is disposed adjacent the DFL sensor, yet spaced from the RHB structure. A second layer of the multilayer structure is a different insulating layer that is disposed adjacent the RHB structure, yet spaced from the DFL sensor. The multilayer structure helps improve areal density without degrading head stability and performance reliability by maintaining RHB coercivity.